Chemistry

Metallurgy – SESSION II

Session Opener

What is sterling silver?

Solid solution of Cu in Ag

Session Objectives

Session objectives

Methods of purification of metals

Metallurgy of Fe, Cu, Ag, Zn, Al

Refining of crude metal

1. Liquation process

Do you know?

Infusible impurity left over during liquationis called as:

Dross

Refining of crude metal

• Based on difference in the boiling point of the impurities and the metal.

• Volatile metals form the vapour first and separated by condensing in a receiver.

2. Distillation:

Refining of crude metal

compressed crude metal

Metal under reduced pressurein electric furnace

Volatile impuritiesMolten metal (chilled to obtain puremetal)

3. Vacuum sublimation method

Refining of crude metal

Oxides are removed from impure metal

Re verbaratory furnace2 2 2 3Cu O Cu SO As O

Melted the metal

4. Furnace refining or poling

Reverbaratory furnace

Refining of crude metal

(5) Zone refining

Direction of trave l

a

ofheater, m olten zone

nd im purities

I m pure germ anium rod

Molten zone(containing im purities)

Recrystallized pure germ anium

Circular heater

Refining of crude metal

250ºC4

Ti taniumtetraiodide

Ti 2l2 Til

1400ºC4 2

Tungstenfilament

Til Ti 2 l

6. Van Arkel method (or Vapour phase refining)

Refining of crude metal

4Impure PureNickelnickel Nickletetracarbonyl

Ni 4CO Ni(CO) Ni 4CO

7. Thermal decomposition method (Carbonyl method, Mond Process)

Refining of crude metal

• Used for purification of silver containing impurity of lead.

• Based on selective oxidation of lead over silver.

• The impure silver is smelted in cupel (dish made of bone ash) in blast of air in reverberatory furnace.

• Lead is oxidised to lead oxide (PbO) and blown away by blast of air.

• The remaining part melts and is absorbed by the bone ash cupel. At the end cupel is covered by silver.

8. Cupellation

Refining of crude metal

9. Electrolytic refining

Electrolytic refining

10. Chromatographic method:

• Based on the difference in the adsorbability of the metal and

the impurities.

• Adsorbent–alumina (Al2O3).

• Eleuent

• Specifically useful for the separation of the elementsavailable in very small amounts.

Ellingham diagram

Metallurgy of Iron

(i) Ore – Haematite (Fe2O3)

(ii) Concentration of ore – by magnetic separation

(iii) Roasting – Moisture, sands are removed as oxide.

(iv)Smelting – Done in blast furnace. Roasted ore, limestone and coke are added in blast furnace for smelting.

Metallurgy of Iron

2 2

2

C O CO 415 kJ

CO C 2CO 162.3 kJ

3 2

2 3Flux Impurity Slag

CaCO CaO CO

CaO SiO CaSiO

Fe O + C + C aC O2 3 3

W asteG ases

S tee l sh e ll

H ot air b lastthrou gh thyeres

Zone of redu ction

C en tra l Zon e

Zone of fus ion

Zone of com bu stion

575 - 975 K

1175 - 1475 K

1475 - 1575 K

1775 - 1800 K

S lagM o lten iron

2 3 2

3 4 2

2

Fe O +CO 2FeO+CO

Fe O +CO 3FeO+CO

FeO+CO Fe+CO

Heat treatment of steel

1. Quenching or hardening

• Process of heating steelto red hot followed by sudden cooling by plunging to oil or water.

• Makes steel hard and brittle due to formation of iron carbide (Fe3C).

2. Annealing

• Process of heating steel to red hot then cooling slowly.

• Annealing makes steel soft and ductile.

Heat treatment of steel

3. Tempering

• Process of heating steel the quenched steel to temperature much below redness followed by slow cooling.

• Tempering retains the hardness but brittleness disappears.

4. Nitriding

• Process of producing hard coating or iron nitride on surface of steel.

Metallurgy of copper

1. Ore – Copper pyrite CuFeS2

2. Concentration — Froth floatation process.

3. Roasting —

2 2 2 2

2 2 2 2

2 2

2CuFeS O Cu S 2FeS SO

2Cu S 3O 2Cu O 2SO (Partly)

2FeS 3O 2FeO 2SO (Partly)

Metallurgy of copper

2 3Slag

FeO SiO FeSiO

Since iron has more affinity for oxygen, therefore FeO is formed first.

2 2Cu O FeS Cu S FeO

Slag is removed from upper layer. Molten mass containing Cu2S and Fe is called copper malte.

Smelting

Metallurgy of copper

Molten matter is mixed with sand (SiO2) and heated in Basemer converter.

2 2

2 3Slag

2FeS 3O 2FeO 2SO

FeO SiO FeSiO

2 2 2 2

2 2 2

2Cu S 3O 2Cu O 2SO

2Cu O Cu S 6Cu SO

Blister copper.

Basemerisation

Refining of copper

By poling of electrolytic refining.

What is matte?

(a) CuO + FeS

(b) CuS + FeO

(c) Cu2S + FeS

(d) None of the above

Metallurgy of Silver

1. Ore — Argentite AgS

2. Concentration — By froth flotation process.

3. Extraction — By Mac Arthur Forrest Process.

2 2 2Sodiumargentocyanide(water so lub le)

2 2 4

Ag S 4NaCN 2Na Ag(CN) Na S

2Na Ag(CN) Zn Na Zn(CN) 2Ag

4. Refining — By electrolytic method.

Illustrative example

Name the metals which areconsumed in elemental form?

Metals consumed in elemental form are Ag and Au.

Metallurgy of Zinc

1. Ore – Zinc blende (ZnS)

2. Concentration of ore — By froth flotation process.

3. Roasting—

2 22ZnS 3O 2ZnO 2SO

4. Conversion of ZnO to Zn

distillationZnO C Zn CO

Vapours of Zn of are collected after distillation.

Illustrative example

Spelter is

(a) 98% Zinc

(b) Pure Zinc

(c) 98% Al

(d) Impure Fe

Metallurgy of Aluminium

1. Ore — Bauxite Al2O3

2. Concentration of bauxite —The method of concentration of bauxite depends on nature of impurity present in it.

Baeyer’s process

Used when impurity is of ferrous oxide.

Baeyer’s process

2 3 2 2Al O 2NaOH 2NaAlO H O

2 2 3(White ppt)

NaAlO 2H O Al(OH) NaOH

3 2 3 2(Pure)

2Al(OH) Al O 3H O

Serpeck’s process

— Used when silica is the chief impurity in bauxite.

Al(OH)3

ImpureBauxite

+ C + N2

DAlN + Silicone (volatile)Aluminiumnitride

+ H2OD

(ppt)

D

Pure Al2O3

Serpeck’s process

2 3 2Aluminiumnitride

Al O 3C N 2AlN 3CO

3 2 3 2(Pure)

2Al(OH) Al O 3H O

2 3 3(Pr ecipitate)

AlN 3H O Al(OH) NH

Hall’s Process

Used when no specific type of impurity is present.

Al(OH)3

Na2CO3

NaOH

ImpureBauxite D

H2O and filtered

D

D

Pure Al2O3

Insoluble impurities (Fe2O3 and others)

Soluble sodium meta-aluminate

Precipitate Solution

Filtered

Hopp’s process

– +

Pure alum inium (cathode)

Cryolyte + BaF (electrolyte)2

Impure Al (Anode)

Impure a lum inium

Iron tank havinglining of graphite

Hopp's process

Electrolysis of pure alumina (Al2O3)

3 6 33

3

Na AlF 3NaF AlF

AlF Al 3F

3

2 3 3 2

At cathode 2Al 6e 2Al

3At anode Al O 6F 2AlF O 6e

2

Question

Thank you